/**
 * NullLiteral.java
 * Copyright (C) 2011 Yuanyan<yuanyan.cao@gmail.com>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
package edu.rabbit.kernel.schema;

import org.antlr.runtime.tree.CommonTree;

import edu.rabbit.schema.INullLiteral;

/**
 * @author Yuanyan<yanyan.cao@gmail.com>
 * 
 */
public class NullLiteral extends Expression implements INullLiteral {

    public NullLiteral(CommonTree ast) {
        assert "null".equalsIgnoreCase(ast.getText());
    }

    @Override
    public String toString() {
        return "NULL";
    }
}
